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Jie Xi, Fangfang Yan, Jiawei Zhou, Zhong-Lin Lu, Chang-Bing Huang; Perceptual Learning Improves Neural Processing in Myopic Vision. Invest. Ophthalmol. Vis. Sci. 2014;55(13):784.
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The quality of visual perception is jointly determined by the quality and efficiency of optical transmission and neural processing in the visual system. As an optical condition that defocuses (blurs) retinal images of distant objects, myopia affects about 70% of teenagers in China and can impact a variety of visual functions if uncorrected. In this study, we tested to what extent spatial vision deficits in myopia can be compensated through perceptual learning.
Twenty myopic subjects were divided into training (N=12, 23.0±1.7yrs) and control groups (N=8, 23.6±2.0yrs). Subjects in the training group took pre-training monocular measurements of the contrast sensitivity function (CSF) and visual acuity (VA) in both eyes, a ten-day training of grating contrast detection near their cut-off spatial frequencies in one eye, and counterbalanced post-training measurements of CSF and VA. Subjects in the control group only participated in the pre- and post- measurements. In addition, refractions were evaluated before and after the experiment. We also adopted the external noise method (Dosher & Lu, 1998) to investigate the mechanism(s) underlying contrast sensitivity improvements in the trained eyes of three observers in the training group.
We found that training 1) improved CS at the trained spatial frequency and VA in both eyes (trained eye: CS by 4.5 dB and VA by 2.6 lines or 5.1dB; untrained eye: CS by 2.4 dB and VA by 2.1 lines or 4.1dB); 2) improved CS over a wide range of spatial frequencies (by 4.0 dB); 3) did not lead to any significant refractive changes; and 4) improved CS through internal noise reduction and external noise exclusion. The improvements in CS and VA were almost fully retained for at least four months in the three subjects tested. To control for potential accommodation effects, we also trained another group of subjects at the distance (5 m) used for visual acuity test for distant vision and found similar results.
These results suggest that neural plasticity in adults with myopia may be exploited in behavioral treatments to compensate for the optical deficits in myopia.
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